1. Field
One embodiment of the present invention relates to a motion picture stream signal conversion technique which can be suitably applied to an information processing apparatus such as a personal computer including a recording function of receiving, for example, digital television broadcast program data and recording the data on disk media.
2. Description of the Related Art
With recent advances in motion picture encoding techniques, information processing apparatuses which process motion pictures as digital signals have become widespread. Recently, people have begun to view/listen to and record digital television broadcast program data on personal computers using software having a function of processing motion pictures.
Under such circumstances, there have been proposed various techniques for efficiently recording motion picture stream signals on disk media such as hard disk drives (HDDs) and Digital Versatile Disks (DVDs) (see, e.g., Jpn. Pat. Appln. KOKAI Publication No. 10 304375).
Assume that the same motion picture encoding scheme such as a scheme using the H.264 format is used for a motion picture stream signal output from a broadcasting state as digital television broadcast program data and a motion picture stream signal recorded as record data on a disk medium. Even in this case, since detailed specifications are independently defined for these signals, re-encoding, transcoding, or the like may be required. A typical example of this is that the maximum GOP length defined on the input side is larger than that on the output side.
A GOP length corresponds to the interval between I-picture frames of three types of frames (I-picture, P-picture, and B-picture frames) defined by various types of motion picture encoding schemes in addition to the H.264 format. An I-picture frame is a picture frame encoded by using only information within an encoding target frame. In contrast, a non I-picture frame, i.e., a P/B-picture frame, is a picture frame encoded by using information outside an encoding target frame (information of a past or future frame).
For a motion picture stream signal as digital television broadcast program data which does not require much consideration of locating the start of a given program, this maximum GOP length is often defined as a relatively large value. In contrast, for a motion picture stream signal as record data which requires consideration of locating the start of a given program, this maximum GOP length is often defined as a relatively small value. Such a situation can occur not only in a case in which a motion picture stream signal output from a broadcasting state is recorded on a disk medium but also in a case in which when a motion picture stream signal recorded on a given disk medium is moved or copied to another disk medium, detailed specifications on the two disk media differ from each other (maximum GOP length on input side>maximum GOP length on output side), even though the media use the same motion picture encoding scheme.
Conventionally, in such a case, all input motion picture stream signals are temporarily decoded (even though the same motion picture encoding scheme is used on both sides), and the decoding results are encoded again, thus performing an enormous amount of conversion processing.